Method of restoring shrunken films



Dec.2-

, 1930. J. a. E. WRIGHT METHOD OF RESTORING SHRUNKEN FILMS Filed June28, 1929 Inventor: James G.E.WT i2 ht, Wm

His Attorney.

Patented Dec. 2, 1930 UNITED STATES PATENT OFFICE JAMES G. E. WRIGHT, OFALILAUS, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATIONOF NEW YORK METHOD OF RESTORING SHRUNKEN FILMS Application filed June28,

My invention relates to celluloid films of the motion picture type whichthrough exposure or age have materially shrunk. It is the object of myinvention to provide an improved process whereby a shrunken film may berestored substantially to its original condition.

Referring to the drawing wherein is shown an apparatus useful incarrying out my invention, Fig. 1 illustrates a film supporting frameand Fig. 2 shows a detail thereof.

A common nitrate celluloid film if exposed when new to ordinaryatmospheric conditions will shrink as much as one sixteenth of an inchper foot during the first weeks exposure. This shrinkage continues at adecreasing rate as time goes on so that in the course of a year thetotal shrinkage may be as much as three sixteenths of an inch per foot.Inasmuch as these films are usual- 1 provided with sprocket toothopenings or engaging with driving sprockets, any variation in the pitchof the tooth openings 1 of the film from the original or correct pitchresults in improper sprocket tooth action. A small amount of shrinkage,as, for example, one sixteenth of an inch per foot, may in the case of aprinter be compensated by a suitable mechanical adjustment of themachine. Such a film also may be passed through the projector withouttrouble but when the shrinkage becomes excessive through age orcontinued exposure to the atmosphere serious difficulty is encounteredwith machines in present use. I have found that films which due to yearsof storage had become so shrunken that they would not feed properlythrough the printer or projector may be restored to their pristinecondition by the method and the apparatus which I shall now describe.

In the accompanying drawing, Fig. 1 illustrates one form of apparatuswhich may be used for carrying my invention into effect and Fig. 2 showsan enlarged view of one detail thereof.

The shrunken film is first wound upon a frame which in its general formis similar to those in common use but differs in that the cross bars areadjustably connected to 1929. Serial No. 374,595.

the end frame so as to permit taking up the subsequent extension of thefilm. In the drawing, the film 1 is shown supported on the frame 2 whichin its general character 1s similar to frames for such purposes incommon use. It comprises the end bars 3 and 4 and the cross bars 5 and 6forming a rectangle over which the film is wound. Cross bar 5 is rigidlysecured to the end bars but cross bar 6 is adjustably attached theretowhereby as the film elongates, the slack can easily be taken up. Asshown in Fig. 2, the upper end of each end bar 3 and 4 is formed with aguide slot 8 which receives an end of the cross bar 6. Near each end thecross bar is provided with the threaded stud 9 which extends up throughthe bracket 10 on the end bar and on which is the winged nut 11. Betweenthe bracket and the cross bar is the coil spring 12.

The shrunken film is wound on the frame in the usual manner with theupper cross bar in its lowermost position. The frame containing the filmis then immersed in a tank of water to soften the gelatine emulsion,otherwise the subsequent swelling of the celluloid would injure it. Thetime required for this softening is the time usually employed when afilm is to be developed, which is approximately one half hour. Whilestill on the frame, the film is then immersed in a solution comprisingalcohol, camphor, and water, and allowed to soak for a number of hoursor until the desired elongation of the film has taken place. In additionto the above I prefer to use a small quantity of ammonia and glycerine,the former neutralizing any acidity of the solution and the latterserving to restore the flexibility of the film. I have obtained verygood results using a solution of the above mentioned ingredients in thefollowing proportions Denatured alcohol 3900 0.0. Camphor 97.5 g.Ammonia (.880 sp. gr.) 49 c. c. Glycerine 195 c. 0. Water 5100 c. c.

I dissolve the camphor in the alcohol and add the ammonia and glycerineand last of .2 greases all the Water. This solution has a specificgravity of .944. With this solution the time required to restore a filmshrunken about three eighths of an inch ier foot was twelve hours. As aresult of soa ing in such a solution the celluloid film swells so thateach loop hangs limp on the frame. The amount of extension of the filmcan easily be measured by comparison with a short piece of unshrunkenfilm or by measuring a few inches of the film with a ruler in which caseeight pictures of standard 35 m. m. film should occupy a length of sixinches of the film. l-Vhen the film has elongated under this treatmentto its original or proper length the movable cross bar of the frame isadjusted by means of the winged nuts to put the film loops under slighttension. The film is then removed and allowed to dry under tension on 30the frame. When dry the film will be found to have not only the correctlength but also the correct width. It is possible to bring the film tothe right length in a much shorter time, for example, in as short a timeas one and one half hours by keepin the film continually under tensionto thereby draw it out. This, however, is objectionable since itdistorts the film with the result that after treatment it is too narrowfor the printing machine or projector. The length of time required forthe swelling of the celluloid is dependent to a certain extent upon therelative amount of camphor in the solution, the strength of the solutiontherefor and the length of time that 5 the film is immersed may bevaried widely from the representative figures which I have given.

WVhat I claim as new and desire to secure by Letters Patent of theUnited States is:

0 1. The process of restoring a shrunken celluloid photographic filmsubstantially to its original length which comprises softening theemulsion on the film, soaking the film in a camphor solution to elongateit, and drying it while maintained in its elongated condition.

2. The process of restoring a shrunken celluloid photographic filmsubstantially to its original length which comprises soaking the film inwater to soften the emulsion thereon,

soaking it in a solution including alcohol,

camphor and water to elongate it, and drying it while mechanicallyrestrained from shrinkage.

3. The process of restoring a shrunken celluloid photographic filmsubstantially to its original condition which comprises soaking the filmin water to soften the emulsion thereon, soaking it in a solutioncontaining alcohol, camphor, ammonia, lycerine and water, --.n anddrying it while mecianically restrained from shrinkage.

In witness whereof, I have hereunto set my hand this 27th da of June,1929.

J: H. S G. E. WEIGHT.

